Use of Phosphate-Reporter Bacteria to Study Phosphate Limitation in the Rhizosphere and in Bulk Soil

1994 ◽  
Vol 7 (1) ◽  
pp. 32 ◽  
Author(s):  
Letty A. de Weger
Keyword(s):  
Bulk Soil ◽  
Phosphate Limitation ◽  
Reporter Bacteria

scholarly journals Non-Conventional Metal Ion Cofactor Requirement of Dinoflagellate Alkaline Phosphatase and Translational Regulation by Phosphorus Limitation

2019 ◽  
Vol 7 (8) ◽  
pp. 232 ◽  
Author(s):  
Xin Lin ◽  
Chentao Guo ◽  
Ling Li ◽  
Tangcheng Li ◽  
Senjie Lin
Keyword(s):  
Alkaline Phosphatase ◽  
Metal Ion ◽  
Translational Regulation ◽  
Organic Phosphorus ◽  
Niche Differentiation ◽  
Phosphorus Limitation ◽  
Marine Phytoplankton ◽  
Phosphate Limitation ◽  
Dissolved Organic Phosphorus ◽  
Metal Cofactor

Alkaline phosphatase (AP) enables marine phytoplankton to utilize dissolved organic phosphorus (DOP) when dissolved inorganic phosphate (DIP) is depleted in the ocean. Dinoflagellate AP (Dino-AP) represents a newly classified atypical type of AP, PhoAaty. Despite While being a conventional AP, PhoAEC is known to recruit Zn2+ and Mg2+ in the active center, and the cofactors required by PhoAaty have been contended and remain unclear. In this study, we investigated the metal ion requirement of AP in five dinoflagellate species. After AP activity was eliminated by using EDTA to chelate metal ions, the enzymatic activity could be recovered by the supplementation of Ca2+, Mg2+ and Mn2+ in all cases but not by that of Zn2+. Furthermore, the same analysis conducted on the purified recombinant ACAAP (AP of Amphidinium carterae) verified that the enzyme could be activated by Ca2+, Mg2+, and Mn2+ but not Zn2+. We further developed an antiserum against ACAAP, and a western blot analysis using this antibody showed a remarkable up-regulation of ACAAP under a phosphate limitation, consistent with elevated AP activity. The unconventional metal cofactor requirement of Dino-AP may be an adaptation to trace metal limitations in the ocean, which warrants further research to understand the niche differentiation between dinoflagellates and other phytoplankton that use Zn–Mg AP in utilizing DOP.

scholarly journals Organic mulching promotes soil organic carbon accumulation to deep soil layer in an urban plantation forest

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Xiaodan Sun ◽  
Gang Wang ◽  
Qingxu Ma ◽  
Jiahui Liao ◽  
Dong Wang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Content ◽  
Fine Roots ◽  
Soil Layer ◽  
Carbon Accumulation ◽  
Bulk Soil ◽  
Organic Mulch ◽  
The Impact ◽  
Soc Fractions

Abstract Background Soil organic carbon (SOC) is important for soil quality and fertility in forest ecosystems. Labile SOC fractions are sensitive to environmental changes, which reflect the impact of short-term internal and external management measures on the soil carbon pool. Organic mulching (OM) alters the soil environment and promotes plant growth. However, little is known about the responses of SOC fractions in rhizosphere or bulk soil to OM in urban forests and its correlation with carbon composition in plants. Methods A one-year field experiment with four treatments (OM at 0, 5, 10, and 20 cm thicknesses) was conducted in a 15-year-old Ligustrum lucidum plantation. Changes in the SOC fractions in the rhizosphere and bulk soil; the carbon content in the plant fine roots, leaves, and organic mulch; and several soil physicochemical properties were measured. The relationships between SOC fractions and the measured variables were analysed. Results The OM treatments had no significant effect on the SOC fractions, except for the dissolved organic carbon (DOC). OM promoted the movement of SOC to deeper soil because of the increased carbon content in fine roots of subsoil. There were significant correlations between DOC and microbial biomass carbon and SOC and easily oxidised organic carbon. The OM had a greater effect on organic carbon fractions in the bulk soil than in the rhizosphere. The thinnest (5 cm) mulching layers showed the most rapid carbon decomposition over time. The time after OM had the greatest effect on the SOC fractions, followed by soil layer. Conclusions The frequent addition of small amounts of organic mulch increased SOC accumulation in the present study. OM is a potential management model to enhance soil organic matter storage for maintaining urban forest productivity.

Alkaline soil pH affects bulk soil, rhizosphere and root endosphere microbiomes of plants growing in a Sandhills ecosystem

2021 ◽  
Vol 97 (4) ◽  
Author(s):  
Lucas Dantas Lopes ◽  
Jingjie Hao ◽  
Daniel P Schachtman
Keyword(s):  
Microbial Communities ◽  
Plant Species ◽  
Soil Ph ◽  
Soil Microbial Communities ◽  
Bulk Soil ◽  
Strong Impact ◽  
Alkaline Soil ◽  
Alkaline Soils ◽  
Soil Microbial ◽  
Soil Rhizosphere

ABSTRACT Soil pH is a major factor shaping bulk soil microbial communities. However, it is unclear whether the belowground microbial habitats shaped by plants (e.g. rhizosphere and root endosphere) are also affected by soil pH. We investigated this question by comparing the microbial communities associated with plants growing in neutral and strongly alkaline soils in the Sandhills, which is the largest sand dune complex in the northern hemisphere. Bulk soil, rhizosphere and root endosphere DNA were extracted from multiple plant species and analyzed using 16S rRNA amplicon sequencing. Results showed that rhizosphere, root endosphere and bulk soil microbiomes were different in the contrasting soil pH ranges. The strongest impact of plant species on the belowground microbiomes was in alkaline soils, suggesting a greater selective effect under alkali stress. Evaluation of soil chemical components showed that in addition to soil pH, cation exchange capacity also had a strong impact on shaping bulk soil microbial communities. This study extends our knowledge regarding the importance of pH to microbial ecology showing that root endosphere and rhizosphere microbial communities were also influenced by this soil component, and highlights the important role that plants play particularly in shaping the belowground microbiomes in alkaline soils.

scholarly journals The Phosin PptA Plays a Negative Role in the Regulation of Antibiotic Production in Streptomyces lividans

Antibiotics ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 325
Author(s):  
Noriyasu Shikura ◽  
Emmanuelle Darbon ◽  
Catherine Esnault ◽  
Ariane Deniset-Besseau ◽  
Delin Xu ◽  
...  
Keyword(s):  
Antibiotic Production ◽  
Streptomyces Lividans ◽  
Positive Control ◽  
Phosphate Limitation ◽  
Antibiotic Biosynthesis ◽  
Nudix Hydrolase ◽  
Energetic Stress ◽  
Accessory Factor ◽  
Negative Role ◽  
Weak Expression

In Streptomyces, antibiotic biosynthesis is triggered in phosphate limitation that is usually correlated with energetic stress. Polyphosphates constitute an important reservoir of phosphate and energy and a better understanding of their role in the regulation of antibiotic biosynthesis is of crucial importance. We previously characterized a gene, SLI_4384/ppk, encoding a polyphosphate kinase, whose disruption greatly enhanced the weak antibiotic production of Streptomyces lividans. In the condition of energetic stress, Ppk utilizes polyP as phosphate and energy donor, to generate ATP from ADP. In this paper, we established that ppk is co-transcribed with its two downstream genes, SLI_4383, encoding a phosin called PptA possessing a CHAD domain constituting a polyphosphate binding module and SLI_4382 encoding a nudix hydrolase. The expression of the ppk/pptA/SLI_4382 operon was shown to be under the positive control of the two-component system PhoR/PhoP and thus mainly expressed in condition of phosphate limitation. However, pptA and SLI_4382 can also be transcribed alone from their own promoter. The deletion of pptA resulted into earlier and stronger actinorhodin production and lower lipid content than the disruption of ppk, whereas the deletion of SLI_4382 had no obvious phenotypical consequences. The disruption of ppk was shown to have a polar effect on the expression of pptA, suggesting that the phenotype of the ppk mutant might be linked, at least in part, to the weak expression of pptA in this strain. Interestingly, the expression of phoR/phoP and that of the genes of the pho regulon involved in phosphate supply or saving were strongly up-regulated in pptA and ppk mutants, revealing that both mutants suffer from phosphate stress. Considering the presence of a polyphosphate binding module in PptA, but absence of similarities between PptA and known exo-polyphosphatases, we proposed that PptA constitutes an accessory factor for exopolyphosphatases or general phosphatases involved in the degradation of polyphosphates into phosphate.

The response of planktonic phosphate uptake and turnover to ultraviolet radiation in Lake Erie

2002 ◽  
Vol 59 (5) ◽  
pp. 778-786 ◽  
Author(s):  
C D Allen ◽  
R E.H Smith
Keyword(s):  
Ultraviolet Radiation ◽  
Lake Erie ◽  
Radiation Treatment ◽  
Phosphate Uptake ◽  
Ultraviolet B ◽  
Phosphate Limitation ◽  
Bacterial Cells ◽  
Near Surface ◽  
Ambient Concentrations ◽  
Uptake Activity

The hypothesis that ambient ultraviolet radiation (UVR), at near-surface intensities, may diminish phosphorus availability to phytoplankton was tested in Lake Erie in July and August of 1998 and 1999. Relative to samples exposed to photosynthetically active radiation (PAR, 400–700 nm) only, those exposed to ultraviolet-B (UVB, 280–320) and (or) ultraviolet-A (UVA, 320–400 nm) in natural sunlight, or kept in darkness, had diminished phosphate uptake rates at elevated (1 µM P) dissolved phosphate concentrations. By contrast, the specific uptake rate of dissolved phosphate at ambient concentrations (turnover rate) was not significantly affected by UVR or darkness. Turnover was usually dominated by particles smaller than 0.8 µm, whereas uptake from elevated concentrations was dominated by larger particles. The size distribution of turnover and uptake activity was not affected by radiation treatment. Chlorophyll a concentrations were decreased by sufficient exposure to UVB and (or) UVA and increased by deprivation of PAR (dark controls), but the concentration of bacterial cells was unaffected. The results showed that UVR inhibited the phosphate uptake potential of larger, probably algal, plankton but did not change the apparent severity of phosphate limitation at ambient concentrations.

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